Stretch and wipe forming method and apparatus with tension control by wipe shoe



n- 1963 F. J. PHILLIPS 3,074,464

STRETCH AND WIPE FORMING METHOD AND APPARATUS WITH TENSION CONTROL BY WIPE SHOE Filed March 28. 1960 V 2 Sheets-Sheet 1.

INVENTOR. FPA NK] PH/AA /P5* BY I h L TTOENEY 1953 F. J. PHlLLlPS 74, 64

STRETCH AND WIPE FORMING METHOD AND APPARATUS WITH TENSION CONTROL BY WIPE SHOE Filed March 28. 1960 2 Sheets-Sheet 2 awn T02. E giAA g J PUMA/P5.

TRETCH AND WIPE FQRMING METHOD AND APPARATUS WITH TENSION CGNTROL BY WIPE SHGE Frank J. Phillips, Cleveland, ()hio, assignor to The Cyril Bath Company, Solon, Ohio, a corporation of Ohio Filed Mar. 28, 1960, Ser. No. 17,931 2 Claims. (Cl. 153-40) This invention relates to a method of combined wipe and stretch forming of metal and to a combined wipe and stretch forming machine and control therefor.

The present invention relates generally to the combined Wipe and stretch forming machines of the general type disclosed in Us. Patent No. 2,514,830, issued July 11, 1950, and includes certain control elements of the general type disclosed in US Patent No. 2,849,048, issued August 26, 1958.

With the combined stretch and wipe forming machines heretofore provided, the conventional practice is to anchor one end of a length of stock in fixed position relative to a turntable on which is fixedly supported a side face die about which the stock is to be formed, and to connect the other end of the stock to a stretch forming head operated by a stretch forming piston and cylinder assemblage. During table rotation and wrapping of the stock about the side face die, yieldable tension sufficient to stretch and permanently elongate the stock is applied to the stock endwise of the stock by the stretch forming assemblage.

Concurrently with the stretch forming of the stock, the stock is pressed against the side face of the die by a wipe forming shoe of the roller or skid type which is applied by yieldable pressure supplied by a wipe forming assemblage. The concurrent stretch forming and wipe forming causes the stock to conform accurately to the side face of the die with little or no objectionable springback. With ordinary steels, the wipe forming forces were not severe relative to tie tensiening forces and could be ignored to a large extent.

Thus, in combined stretch and wipe forming of stock in this manner, the practice is to maintain sufiicient tension on the stock by the stretch forming assemblage to stretch form and permanently elongate it independently of any forces imposed by the wipe forming shoe.

In the above US. Patent No. 2,849,048, a certain modification is made by virtue of controls which combine a signal from the stretch forming assemblage and which is related to the direct tension applied thereby, and a flexure signal from the wipe forming assemblage and which is related to the component of tension applied to the stock due to drag of the shoe on the stock during wipe forming. The signal from the wipe forming assemblage moderates to some extent the signal from the stretch forming assemblage in relation to the forming pressure applied by the wipe forming assemblage. This provides more accurate control in those instances in which heavy wipe forming pressures are employed, or in which higher alloys, with a yield point close to ultimate strength, necessitate more accurate control of the stretching forces. Again, the higher alloys require higher wipe forming pressures.

However, in this operation, the tension applied by the stretch forming assemblage alone remains the primary tensioning force, the wipe forming pressure being only that required for Wipe forming. Any tensioning component of the wipe forming forces is incidental and is allowed for in the control of the stretch forming assemblage.

In accordance with the present invention, the stock is formed by a new method wherein it is tensioned primarily by the Wipe forming assemblage, the tension applied by the stretch forming assemblage, endwise from the point of instantaneous contact or tangency of the stock with the side face die to that end of the stock which is connected to the stretch forming assemblage, being much below the tension which can cause permanent deformation of the stock. The Wipe forming shoe is applied under a pressure beyond that required merely for wipe forming so that, at the instantaneous point of contact, the metal is subjected to a large endwise tensioning component of force by the drag of the shoe end- Wise of the die face. This component is to a degree such that stretch forming tension is produced at that particular point of contact, the tension being a result of the direct tension below elastic limit applied by the stretch forming assemblage plus the component of force endwise of the stock deliberately imposed by the frictional drag or other tensioning components of the Wipe shoe thereon. This permits the use of pressure fluid at more nearly constant pressure in the stretch forming assemblage, leaving tension control a function of variability in the pressure of fluid supplied to the wipe forming assemblage.

As a result, different operating efiects on the metal and different forming procedures are possible.

Further, the invention is directed to an apparatus for this purpose by which the stretch forming piston and cylinder assemblage is set for a predetermined continuous tension so far below the elastic limit of the stock that no permanent elongation of the stock can result. This force is low enough so that variations due to friction and binding stresses in the stretch forming assemblage do not increase it to the elastic limit of the stock. 6n the other hand, means are provided for controlling tension by the signal from the wipe forming shoe which is in relation to the pressure with which the shoe is applied to the stock and hence in relation to the resistance of the stock to the drag of the shoe. By controlling the wipe shoe with this signal, the tensioning force on the stock created by the shoe, substantially at the instantaneous line of contact of the stock, die, and shoe, plus the relatively constant or lower tension applied by the stretch forming assemblage, provides the necessary tensioning force, but at this particular point only, to stretch the stock permanently.

Further objects and advantages will become apparent from the following description wherein is illustrated a preferred embodiment of my invention, and in which:

FIG. 1 is a top plan view of an apparatus adapted for carrying out the present invention, the hydraulic diagram and control diagram being shown thereon for clearness in illustration;

FIGS. 2 and 3 are a front elevation and a left end elevation, respectively, of the apparatus shown in FIG. 1, the control system being omitted for clearness in illustration; and

FIG. 4 is a diagrammatic illustration of the apparatus illustrating certain phenomenon in the formation of the metal thereby.

Referring to the drawings, the apparatus comprises a frame 1 on which a turntable 2 is mounted for rotation about the axis of an upright post 3. The turntable has a suitable ring gear 4' driven by a pinion gear 5 which, in turn, is driven by a speed reduction transmission 6. The transmission 6 is driven by a hydraulic motor 7 to which pressure fluid is supplied by a pump 8.

Mounted on the frame 1 is a stretch forming piston and cylinder assemblage 10 including a cylinder 11 and a piston 12 having a piston rod 13. The assemblage 10 is supported on the frame 1 for swinging about an upright axis 14. A slide 15 is connected to the piston rod 13 and is mounted for sliding parallel to the axis of the cylinder 11. At its forward end, the slide 15 has a pedestal suppb'it 16 to which a Stretch head 17 is connected, the stretch head being arranged'f or clamping engagement with one end of a length of stock S for applying tension thereto e'ndwise of the stock.

The other end of the length of stock is connected for rotation in fixed position relative to the table 2 and a 'sideface die D by means of a clamp 18 on the table so that, by rotation of the table 2, the stock can be wrapped about the die D while held under tension endwise by the stretch forming assemblage 10.

Also mounted on the frame 1 is a wipe forming assemblage 20 including a cylinder 21 and a piston 22 having a rod 23. A slide 24 is mounted for sliding movement parallel to the axis of the cylinder 21 and at its forward end is provided with a pedestal 25 to which is connected a load cell 26 which, in turn, carries a Wipe forming shoe 27. The load cell 26 is relatively stifi for resisting movement of the shoe 27 ina direction parallel to the axis of the table. The cell can be deflected readily in a direction normal to a plane defined by the table axis and the axis of the cylinder 21. p

Flexure of the load cell is a result of thefdrag of the wipe shoe 27 against the stock during the wipe forming operation. This drag tends to flex the load cell normal to said plane in the direction toward the stretch forming assemblage.

In wipe forming, this stress is generally always in the same direction because of the unidirectional movement of the die during table rotation.

"Mounted on one face of the load cell 26 so as to reflect the flexure thereof is a signal indicating device 28. This signal indicating device may be any of the conventional devices but preferably is one of the patch type strain gauges, disclosed in the above United States Letters Pat- E'nt No. 2,849,048, and arranged in a manner therein set orth.

I The stretch forming cylinder 11 is connected to a source of pressure fluid through a suitable control valve 30 which may be remotely controlled by solenoids 31. The valve is operative in one position to direct the pressure fluidto the rod end of the cylinder for applying tensioning force and, concurrently, to connect the head end of the cylinder to a sump, and for reversing the connection as desired. Pressure fluid is supplied to the valve from a suitable pump 32 driven by a motor 33, the output of which can be adjusted by a remote manual control valve 34. The supply of pressure to the valve 30 is through a variable pressure relief valve 35 which may be pre-set to deliver the pressuredesired. In the present instance, this valve is setso that the pressure delivered to the cylinder is below that which is necessary to stretch form or permanently elongate the stock.

In addition, for smoothness in operation, a suitable throttle valve 36 is connected to the rod end of the cylinder '11, the same being controlled by a manual adjustment 37. For example, it may be desirable to set the variable pressure relief valve 35 to deliver a pressure less than that required to stretch form the stock and then set the throttle valve 36 so as to maintain a pressure in the head end of the cylinder 11 substantially less than that for which the valve 35 is set, thus assuring that the tension applied 'bythe stretch forming assemblage cannot reach that required to stretch form the stock.

Referring next to the wipe forming assemblage, pressure fluid is supplied to the assemblage by the pump 32 through a suitable control Valve 40 which is remotely operated by solenoids -41 and which, in one position, applies pressure fluid to the head end of the Wipe forming cylinder 21 and in another position supplies pressure fluid to the rod end. Between the valve 40 and the head end of the cylinder 21 is a variable pressure relief valve 42 which controls the pressure with which the wiping shoe 27 is applied to the stock being laid onto the side face of the 9, Th Variable pressure relief valve is-controlled by a suitable servo-motor 43 whic in turn, is Controlled by an electronic control unit 44. The device or strain gauge 28 is connected to the control unit 44 so that the signals delivered by the control unit for the control of the servomotor 43 are responsive to the signals from the strain gauge 28 and hence to the deflection of the load cell 26. Since this deflection represents the additional tensioning force due to the drag of the shoe on the stock, the pressure supplied to the head end of the cylinder 21 is controlled in response to this signal in such a manner that it applies to the stock a component of tension which is itself above the elastic limit and sufiicien't to stretch form the stock or which is suflicient, when supplemented by the pull of the stretch forming assemblage, to stretch form the stock. This stretch forming tension is applied substantially at the instantaneous line of contact of the stock with the wipe shoe 27, the tension-at all other locations along the stock being less than that required for stretch forming. 7

Referring to FIG. 4, this point of instantaneous contact is indicated at x, the length of stock between the clamp 18 and the point x is indicateat z, and the length of stock between the point x and the stretch forming head 17 is indicated at y. The tension at x, by virtue of the control of the wipe forming shoe, is maintained at the tension desired for stretch forming the stock and is at or'above the elastic limit. The tension at y is much below the elastic limit or below that necessary to permanently elongate the stock. The tension at z is less than the tension at 1': because the stock thins down as it passes the point x under the shoe 27 and hence the drag of the shoe does not appreciably afiect the portion of the stock z. Instead, the metal is caused to flow by the wipe shoe and therefore is in a semi-plastic state directly at the point x. 7 Also the wipe shoe pressure is concentrated substantially on the line of contact and therefore the metal is effectively, fr'ic'tionally held against the side face of the die at-x with frictional resistance adequate to prevent movement of the stock along the side face of the die. As a result the wiping operation does not cause appreciable tension in the portion z.

Thus, in accordance with the present invention, the travel of the head 17 plus the total stretch is equal to the length of the side face of the die and, at any instant Al, the increment of length of the side face of the die, equals At, the increment of travel at that instant, plus As, the increment of stretch.

Accordingly, with the present structure and method, the stock is tensioned from the end which is not connected with the die to the instantaneous point of Wiping contact with a degree of tension such that it does not produce any permanent elongation of the stock. On the other hand, sufficient wipe forming pressure is applied to cause a component of tensioning force which is applied to the stock and which, in combination with the tension applied by the stretch forming head 17,'causes permanent stretching and elongation of the stock at the instantaneous line of contact of the shoe 28 and stock. Accordingly, the tensioning of the stock to the degree necessary for stretch forming is due to the wipe shoe and is controlled primarily by variation in-the pressure of application of the wipe shoe to the stock.

Having thus described my invention, *1 claim:

1. The method of forming a length of metal stock progressively about a side face die and comprising holding the stock at one location in fixed position relative to'the die, applying to the stock at one end of the stock spaced from said one location and from the die a direct tensioning force, said force being of a magnitude insuflicient to tension the stock up to the elastic limit, for tensioning the stock at least between said end-and the instantaneous line of contact of the stock and die, and, while maintaining said direct tensioning force at said magnitude, swinging the stock into contact with the side face of the die progressively toward said end and concurrently-applying high pressure against the stock in a direction toward, the

die progressively therealong at the instantaneous line of contact so as to force the stock against the die face and create at said instantaneous line of contact a component of tensioning force directed toward said end and which component, combined with said direct tensioning force, imposes on the stock at said instantaneous line of contact a resultant combined tensioning force which tensions the stock above its elastic limit and permanently elongates the stock.

2. A method according to claim 1 wherein said direct 10 References Cited in the file of this patent UNITED STATES PATENTS Hein et a1 Dec. 17, 1957 Curtner Aug. 26, 1958 

1. THE METHOD OF FORMING A LENGTH OF METAL STOCK PROGRESSIVELY ABOUT A SIDE FACE DIE AND COMPRISING HOLDING THE STOCK AT ONE LOCATION IN FIXED POSITION RELATIVE TO THE DIE, APPLYING TO THE STOCK AT ONE END OF THE STOCK SPACED FROM SAID ONE LOCATION AND FROM THE DIE A DIRECT TENSIONING FORCE, SAID FORCE BEING OF A MAGNITUDE INSUFFICIENT TO TENSION THE STOCK UP TO THE ELASTIC LIMIT, FOR TENSIONING THE STOCK AT LEAST BETWEEN SAID END AND THE INSTANTANEOUS LINE OF CONTACT OF THE STOCK AND DIE, AND, WHILE MAINTAINING SAID DIRECT TENSIONING FORCE AT SAID MAGNITUDE, SWINGING THE STOCK INTO CONTACT WITH THE SIDE FACE OF THE DIE PROGRESSIVELY TOWARD SAID END AND CONCURRENTLY APPLYING HIGH PRESSURE AGAINST THE STOCK IN A DIRECTION TOWARD THE DIE PROGRESSIVELY THEREALONG AT THE INSTANTANEOUS LINE OF CONTACT SO AS TO FORCE THE STOCK AGAINST THE DIE FACE AND CREATE AT SAID INSTANTANEOUS LINE OF CONTACT A COMPONENT OF TENSIONING FORCE DIRECTED TOWARD SAID END AND WHICH COMPONENT, COMBINED WITH SAID DIRECT TENSIONING FORCE, IMPOSES ON THE STOCK AT SAID INSTANTANEOUS LINE OF CONTACT A RESULTANT COMBINED TENSIONING FORCE WHICH TENSIONS THE STOCK ABOVE ITS ELASTIC LIMIT AND PERMANENTLY ELONGATES THE STOCK. 